Stabilization of metal oxide dispersions



United States Patent O 3,547,605 STABILIZATION F METAL OXIDE DISPERSIONS Thomas E. Cornelius IH, Coraopolis, and Alan E. Bischof,

Pittsburgh, Pa., assignors to Calgon Corporation, Pittsburgh, Pa. No Drawing. Filed Aug. 5, 1968, Ser. No. 749,979 Int. Cl. Cl 1/18, 9/00 U.S. Cl. 44-4 3 Claims ABSTRACT OF THE DISCLOSURE Lecithin, particularly soya lecithin, will act as a dispersant for metal oxides in fuel oil in the presence of fatty acids.

BACKGROUND OF THE INVENTION In U.S. Pats. 3,205,053 and 3,231,592, Andrew T. McCord describes compositions and methods for making dispersions of metal oxides in fuel oil. He employs various fatty acids to disperse the metal oxides. The purpose of the dispersion is to stabilize the metal oxide so that it can inhibit vanadium slag deposition and corrosion on heat exchangers when added to a fuel oil for burning in an industrial or utility boiler. However, experience has shown that the fatty acid-metal oxide complexes used are not stable in their original fuel oil media.

British Pat. 761,378 mentions that lecithin is an oilsoluble organic phosphorous compound which may be used to disperse a substantially dry, solid inorganic material in a high ash residual fuel oil; however, it is not shown that lecithin is most beneficial when used together with a fatty acid, nor indeed is any specific concentration or range of concentrations suggested.

SUMMARY OF THE INVENTION We have found that the addition of small amounts of lecithin to fatty acid dispersions of metal oxides in fuel oil will greatly enhance the stability characteristics of the fatty acid dispersions. The small amounts we may employ render the dispersions thixotropic yet pumpable and very easily handled. The lecithins may be described as digly- Patented Dec. 15, 1970 The structure may also be written as follows:

OHzOOOR CHOOOR See the Merck Index, 8th Ed., p. 615. R may be as described above. It has been observed (The Condensed Chemical Dictionary, 7th Ed., p. 552) that the fatty acid in the {3-position is, as a general rule, an unsaturated fatty acid such as oleic acid and the one in the alpha position is usually saturated such as palmitic.

Commercial lecithins are mixtures within the above structural formula, the fatty acids running from 12 to 22 carbon atoms. However, most commercial lecithin is derived from the soybean, and generally does not contain any saturated fatty acid, although one of the fatty acid groups may be less unsaturated than the other (Kirk-Othemer, Encoyclopedia of Chemical Technology, 2nd ed. vol. 12, 345).

Throughout this specification and claims, the term lecithin is intended to means lecithin such as derived from soybeans, including associated phosphatides, oils, cephalin, and the like normally found in commercial soybean lecithin.

Our metal oxide compositions including lecithin as a dispersant may be used to treat waste fuels such as coke oven gas, sugar cane, and paper mill pulp waste, to inhibit the corrosive effects and tendency to deposit slag caused by sulfur and the non-combustible components of the fuel, particularly vanadium. It is also applicable to coal, lignite and other solid fuels as well as conventional fuel oil. Our invention enables a greater metal oxide content to be used in a more easily handled form which is far more stable than such compositions heretofore. The total quantity of dispersant may be far less than the amount of fatty acid alone required to achieve a comparable but less stable effect.

Our invention will be illustrated by the following table, which shows the results of an experiment performed to demonstrate its effect.

TABLE I.EFFECT OF VARIOUS COM'BINATIONS OF OLEIC ACID AND LEOITHIN IN DISPERSING 100 PARTS MgO IN 100 PARTS #2 FUEL OIL Oleic Separation on standing Example acid, Lecithin, Appearance at time of original No. parts parts mixing procedure 9 days 20 days 1 controL- 4 Very fluid; easy to disperse. Soft to bottom; l sediment; V oil on Solid throughout; 46 oil on top.

top.

2 0 4 Mixed very well; more viscous than Soft to bottom; slightly thixotropic; Therewasmore separation than others;

some mixes. slight separation. lfilougever sediment in bottom fairly 3 2 2 Thixotropic mixture formed; slight Slight oil separation iz"; thin to bot- Thixotropic, very little change; thin gelt ot i standing; very thin with torn with slight sediment. to bottom; fluid on mixing. agi a ion.

4 2 0.30 Thick at start of mixing; continued Very slight separation; good thixo- Very little change; no settling on high speed mixing caused desired tropic mix. bottom; very slight oil on top. thixotropic properties.

5 1 1. 32 This was a thicker mix originally but Slight separation; thixoti'opic. Very little change; thixotropie; slight with continued mixing thisotropie gel formed.

separation.

where OCR and OCR are fatty acid radicals including stearic, palmitic, oleic, linoleic, etc.

In several other experiments of a similar nature, it was further confirmed that less separation occurred whenever lecithin was used together with a fatty acid dispersant.

Thus it may be seen that our invention includes compositions in the following ranges of parts by weight:

Metal oxide 100 Oil medium -125 Fatty acid 0.25-5.0 Lecithin 0.1-3 .0

Generally, it includes a dispersant comprising lecithin and fatty acid in a Weight ratio of from about :1 to about 1:1.

In the above general composition, we intend to include within the term metal oxide magnesium oxide, and/or any other alkaline earth metal oxide. Specifically those oxides contemplated are calcium, magnesium, aluminum, titanium, zirconium, and strontium. Generally speaking, relatively small particle sizes of metal oxide may be most conveniently dispersed with concentrations of dispersant on the higher end of this range.

As an oil medium we may use any combustible or fuel oil, typically kerosene. Fuel oils with higher viscosities may also be used; of these, #2 fuel oil is preferred of all fuel oils.

The fatty acid dispersives useful in our invention are fatty acids containing 10 to 22, preferably 16 to 22 carbon atoms. They may be combined with lecithin prior to mixing in the fuel oil.

We do not intend to be restricted to the specific illustrations and examples recited above. Our invention may be otherwise practiced within the scope of the following claims.

We claim:

1. Composition useful for treating fuel oil and solid fuels to inhibit slag and corrosion in heat exchangers where the fuel is burned comprising, in parts by weight:

(a) as a base, 75 to 125 parts of a combustible oil,

(b) 100 parts metal oxide of the group consisting of calcium, magnesium, aluminum, titanium, zirconium, 30

and strontium,

(c) 0.25 to 5.0 parts fatty acid, and

(d) 0.1 to 3.0 parts lecithin.

2. A dispersant for metal oxides to be used to inhibit slag and corrosion caused by vanadium or sulfur in fuel oil, comprising lecithin and fatty acid in a weight ratio of from about 10 to l to about 1 to 1.

3. Composition useful for inhibiting slag and corrosion during the combustion of fuel oil containing vanadium or sulfur comprising parts by weight metal oxide of the group consisting of calcium, magnesium, aluminum, titanium, zirconium, and strontium, 75 to parts combustible oil, 0.25 to 3.0 parts fatty acid containing 16 to 22 carbon atoms, and 0.1 to 3.0 parts lecithin.

References Cited UNITED STATES PATENTS 2,165,651 7/1939 Rees et a1. 4466 2,176,879 10/1939 Bartell 4451 2,207,430 7/ 1940 Burk et al 4466 2,808,320 10/1957 Rudel et al 44-66 2,991,163 7/1961 Sipos et al 4466 3,020,134 2/ 1962 Keller et a1. 4466X 3,205,053 9/1965 McCord 4466 PATRICK P. GARVIN, Primary Examiner C. F. DEES, Assistant Examiner U.S. Cl. X.R. 4466, 67 

